**3. Results**

Forest composition of unburned stands was dominated by conifers, with slightly more than 75% of the tree basal area belonging to eastern white pine and other conifers, mostly spruces (**Table 2**). Balsam fir represented less than 10% of tree basal area, and broadleaved trees slightly more than 15%. Prescribed burnings significantly

#### *Protected Areas, National Parks and Sustainable Future*


#### **Table 2.**

*Comparison of average (± S.E.) initial tree basal area and sapling density (before burning) and of the % of recent mortality of different species in burned and unburned stands. Student t-tests were used to compare mortality averages between treatments (significant ones are in bold).*

increased the mortality of balsam fir and broadleaved trees, with respectively 38.2 and 39.0% compared with 3.7 and 14.3% in unburned stands (**Table 2**). Mature eastern white pine trees and other conifers were not significantly affected by the burning treatment, except in the 1999 burn which was the most intense (**Table 1**). Eastern white pines were well distributed among DBH classes, with maximum densities recorded between 20 and 60 cm of DBH (**Figure 3A** and **B**). However, small balsam fir trees (≤20 cm) as well as saplings outnumbered eastern white pines (**Figure 3C** and **D**). Balsam fir saplings represented 80% of total sapling density while eastern white pine represented only 0.9% (**Table 2**).

Saplings of balsam fir and broadleaved species were significantly affected by the burning treatment (**Table 2**; **Figure 4**). Mortality averaged 67.4 and 37.0% respectively for balsam fir and broadleaved saplings in burned stands compared with 9.2 and 6.1% in unburned stands (**Table 2**). The most severely burned stand (1999) had killed 93% of the balsam firs, which was 25% higher than in any other burned stand. Overall, mortality of saplings was significantly higher in burned stands (63.6%) than in unburned ones (9.2%) (**Table 2**). However, after burning, the density of balsam fir saplings was still high, mostly because patches of the forest remained unburned in some stands (**Figure 3C**).

Eastern white pine seedling density was lower than for balsam fir in each height class observed in unburned stands (**Figure 3F**) and they represented only 26.7% of all seedlings (**Table 3**). Moreover, they never reached more than 75 cm in height (**Figure 3F**). Prescribed burnings increased the density of eastern white pine seedlings significantly when compared with unburned stands (**Table 3**), their proportion increasing from 26.7 to 83.7% of all seedlings in burned stands. By contrast, the proportion of balsam fir seedlings decreased from 39.6% in unburned stands to 20.6% in burned ones (**Table 3**). However, eastern white pine seedlings were largely dominant in the first five height classes (1–25 cm), but they rarely exceeded 50 cm. Balsam fir seedlings were more evenly distributed up to 130 cm and dominated eastern white pine seedlings in all height classes higher than 25 cm (**Figure 3E**).

No distinctive pattern in eastern white pine seedling growth was obvious along the burning chronosequence. Stands burned in 2004 and 2005 only harboured 417 seedlings of eastern white pine per hectare because these sites (1–2 years after burning) had not yet benefited from a good seed production year [48, 49].

**45**

**Figure 4.**

*Prescribed Burning to Restore Eastern White Pine Forests of La Mauricie National Park…*

C. Saplings – Burned stands D. Saplings – Unburned nburnedstands

9-20 21-40 41-60 61-80 81-100 **DBH (cm)**

B. Trees – Unburned nburnedstands

1-25 26-50 51-75 76-100 101-130 **Height (cm)**

1.1 - 3 3.1- 6 6.1- 9

**DBH (cm) DBH (cm)**

E. Seedling Seedlings – Burned stands F. Seedling Seedlings – Unburned nburnedstands

*Comparisons of eastern white pine (black bars) and balsam fir (grey bars) tree (A and B), sapling (C and D), and seedling (E and F) densities (mean ± S.E.) between burned (n = 7) and unburned white pine stands* 

*Photo showing abundant competing balsam fir seedlings and their reduction 1 year after a prescribed burning* 

*in an eastern white pine stand at Lac Guilinette of La Mauricie National Park of Canada.*

*DOI: http://dx.doi.org/10.5772/intechopen.86224*

A. Trees – Burned stands

1.1 - 3 3.1- 6 6.1- 9

1-25 26-50 51-75 76-100 101-130 **Height (cm)**

*(*n *= 9) of La Mauricie National Park of Canada.*

9-20 21-40 41-60 61-80 81-100

**DBH (cm)**

**Figure 3.**

**r e**

 **/ ha**

**b**

**n**

**uN**

*Prescribed Burning to Restore Eastern White Pine Forests of La Mauricie National Park… DOI: http://dx.doi.org/10.5772/intechopen.86224*

#### **Figure 3.**

*Protected Areas, National Parks and Sustainable Future*

represented only 0.9% (**Table 2**).

**Table 2.**

remained unburned in some stands (**Figure 3C**).

*mortality averages between treatments (significant ones are in bold).*

pine seedlings in all height classes higher than 25 cm (**Figure 3E**).

increased the mortality of balsam fir and broadleaved trees, with respectively 38.2 and 39.0% compared with 3.7 and 14.3% in unburned stands (**Table 2**). Mature eastern white pine trees and other conifers were not significantly affected by the burning treatment, except in the 1999 burn which was the most intense (**Table 1**). Eastern white pines were well distributed among DBH classes, with maximum densities recorded between 20 and 60 cm of DBH (**Figure 3A** and **B**). However, small balsam fir trees (≤20 cm) as well as saplings outnumbered eastern white pines (**Figure 3C** and **D**). Balsam fir saplings represented 80% of total sapling density while eastern white pine

*Comparison of average (± S.E.) initial tree basal area and sapling density (before burning) and of the % of recent mortality of different species in burned and unburned stands. Student t-tests were used to compare* 

Saplings of balsam fir and broadleaved species were significantly affected by the burning treatment (**Table 2**; **Figure 4**). Mortality averaged 67.4 and 37.0% respectively for balsam fir and broadleaved saplings in burned stands compared with 9.2 and 6.1% in unburned stands (**Table 2**). The most severely burned stand (1999) had killed 93% of the balsam firs, which was 25% higher than in any other burned stand. Overall, mortality of saplings was significantly higher in burned stands (63.6%) than in unburned ones (9.2%) (**Table 2**). However, after burning, the density of balsam fir saplings was still high, mostly because patches of the forest

Eastern white pine seedling density was lower than for balsam fir in each height class observed in unburned stands (**Figure 3F**) and they represented only 26.7% of all seedlings (**Table 3**). Moreover, they never reached more than 75 cm in height (**Figure 3F**). Prescribed burnings increased the density of eastern white pine seedlings significantly when compared with unburned stands (**Table 3**), their proportion increasing from 26.7 to 83.7% of all seedlings in burned stands. By contrast, the proportion of balsam fir seedlings decreased from 39.6% in unburned stands to 20.6% in burned ones (**Table 3**). However, eastern white pine seedlings were largely dominant in the first five height classes (1–25 cm), but they rarely exceeded 50 cm. Balsam fir seedlings were more evenly distributed up to 130 cm and dominated eastern white

No distinctive pattern in eastern white pine seedling growth was obvious along the burning chronosequence. Stands burned in 2004 and 2005 only harboured 417 seedlings of eastern white pine per hectare because these sites (1–2 years after burning) had not yet benefited from a good seed production year [48, 49].

**44**

*Comparisons of eastern white pine (black bars) and balsam fir (grey bars) tree (A and B), sapling (C and D), and seedling (E and F) densities (mean ± S.E.) between burned (n = 7) and unburned white pine stands (*n *= 9) of La Mauricie National Park of Canada.*

#### **Figure 4.**

*Photo showing abundant competing balsam fir seedlings and their reduction 1 year after a prescribed burning in an eastern white pine stand at Lac Guilinette of La Mauricie National Park of Canada.*


#### **Table 3.**

*Comparison of living sapling and seedling densities (after burning) of Eastern white pine and balsam fir in burned (n = 5; 2004–2005 excluded) and unburned sites (n = 9).*

#### **Figure 5.**

*Distribution of eastern white pine and balsam fir seedlings among 5-cm height classes in burned stands of various ages in La Mauricie National Park of Canada. No eastern white pine seedling exceeded 45 cm of height.*

**47**

*Prescribed Burning to Restore Eastern White Pine Forests of La Mauricie National Park…*

The stand burned in 2003 (3 years) was exposed to a good seed crop the summer after the treatment and regeneration was the most plentiful in the 5- to 10-cm height class. The stand burned in 2001 (5 years) was exposed to a good seed crop 2 years after the treatment and seedlings were slightly more abundant than in the stand burned in 2003, with almost all seedlings being found in the 5- to 10-cm height class (**Figure 5**). In the stand burned in 1999 (7 years), eastern white pine seedlings were asymmetrically distributed to the right of the 5- to 10-cm height class, with seedlings reaching 25–30 cm (**Figure 5**). However, the stand burned in 1997 (9 years), which benefited from two good seed crops (1998, 2003), did not harbour more eastern white pine seedlings than the other stands, with its seedlings being mainly found in the first two height classes (1–5 cm and 5–10 cm) (**Figure 5**). In the oldest burned stand (1995; 11 years) that benefited from three good seed crops, seedlings were mainly found in the first two height classes. However, eastern white pine seedlings reached their maximum height (40–45 cm) in this stand. Balsam fir seedlings <50 cm high were not abundant in any of these five burned stands compared with eastern white pine seedlings, the only one showing more than 10,000 balsam fir seedlings/ha being the one that burned in 1997 (**Figure 5**).

Prescribed burnings carried out in La Mauricie National Park of Canada killed 38 and 67% of competing balsam trees and saplings respectively and increased eastern white pine seedling density up to an average of 21,133 seedlings/ha, compared with 5135 seedlings/ha in unburned stands. This is higher than the 12,000 seedlings/ ha reported 5 years after small scale (0.2 ha) prescribed burning trial done in an eastern white pine stand at the Petawawa forest research station located in Ontario [41]. Stands burned in 2004 and 2005 had very low density of eastern white pine seedlings when compared with other burned stands because no seed crop occurred after the treatment was applied and the time of our study. However, in these stands, the bracken fern species (*P. aquilinum*) was abundant with an average cover of 26%*.* This fern is highly competitive in recolonizing burned stands when it is present prior to treatment. It is a fire-adapted species that possesses deep fire-resistant rhizomes [50]. Bracken ferns are strong competitors for light and their presence is known to increase the level of competition for the establishment of eastern white pine seedlings [13]. In the future, after a first good seed crop, it would be important to monitor and measure the regeneration of eastern white pine and the effect of the abundance of this fern on pine dynamics. The production of a good seed crop is important after fire or a burning treatment in order to establish strong pine regeneration. Moreover, the succession of various events may also be favourable to establish pine regeneration as described by Lynham and Curran [51]. They reported 50,000 red and white pine seedlings per hectare 5 years after a low-intensity natural fire followed by a good seed crop 2 years later and a blowdown 4 years after the fire. This generated optimal conditions for regenerating pines. Such condition may explain why one of our unburned stand, which was located on an island, had a high density of eastern white pine saplings (100/ha) even though its seedling density was rather low (625/ha). This stand had been disturbed by a small blowdown due to its location on an island. Gaps produced in the forest cover were large enough to favour the growth of eastern white pine seedlings up to the sapling stage. This is important for eastern white pine forest renewal as Stiell [52] demonstrated that pine's ability to compete is greatly improved when the sapling stage is reached. However, even if all the saplings recorded in our unburned stands would reach the canopy, their num-

bers would still remain below the density objective of 100/ha [40].

*DOI: http://dx.doi.org/10.5772/intechopen.86224*

**4. Discussion**

*Prescribed Burning to Restore Eastern White Pine Forests of La Mauricie National Park… DOI: http://dx.doi.org/10.5772/intechopen.86224*

The stand burned in 2003 (3 years) was exposed to a good seed crop the summer after the treatment and regeneration was the most plentiful in the 5- to 10-cm height class. The stand burned in 2001 (5 years) was exposed to a good seed crop 2 years after the treatment and seedlings were slightly more abundant than in the stand burned in 2003, with almost all seedlings being found in the 5- to 10-cm height class (**Figure 5**). In the stand burned in 1999 (7 years), eastern white pine seedlings were asymmetrically distributed to the right of the 5- to 10-cm height class, with seedlings reaching 25–30 cm (**Figure 5**). However, the stand burned in 1997 (9 years), which benefited from two good seed crops (1998, 2003), did not harbour more eastern white pine seedlings than the other stands, with its seedlings being mainly found in the first two height classes (1–5 cm and 5–10 cm) (**Figure 5**). In the oldest burned stand (1995; 11 years) that benefited from three good seed crops, seedlings were mainly found in the first two height classes. However, eastern white pine seedlings reached their maximum height (40–45 cm) in this stand. Balsam fir seedlings <50 cm high were not abundant in any of these five burned stands compared with eastern white pine seedlings, the only one showing more than 10,000 balsam fir seedlings/ha being the one that burned in 1997 (**Figure 5**).
